The present invention relates generally to a transmission gear shifting assembly and, in particular, to an interlock mechanism for inhibiting shifting of more than one shift rail at a given time.
Multi-speed change gear transmissions of both the sliding gear and the sliding clutch type, and the shifting mechanisms for the selective shifting thereof, are well known. In the sliding gear type, selected gears are moved into meshing engagement with other gears and, in the sliding clutch type, constantly meshed gears are selectively coupled to a shaft by means of a slideable clutch. In such transmissions, the slideable gear or clutch member is typically provided with a groove in which a shift fork or other shifting member is received for imparting a selected axial movement thereto. The shift forks are carried by, or at least selectively axially moved by, an axially moveably shift rail or bar.
The shift rails typically have an axially centered neutral position and are moveable in a first and possibly a second axial direction to engage a selected gear. Accordingly, in transmissions of this type, one shift rail is required for at least every pair of selectively engageable gears. Generally, the plurality of axially moveable shift rails are supported in spaced apart, parallel relationship, usually within and near the top of the transmission housing.
In most multi-speed transmissions of the type described above, in order to prevent damage to the gearing and/or clutch components, it is important that only one shift rail be permitted to move from its neutral position at any one time. Accordingly, most manual transmissions incorporate some type of interlock mechanism to inhibit movement of more than one shift rail at a given time. In most interlock mechanisms, movement of any one of the shift rails from its neutral position actuates a locking component which in turn is coupled to block any axial movement of the other shift rails until the one shift rail has been returned to a neutral position.
Many various types of shift rail interlock mechanisms have been proposed. For example, U.S. Pat. Nos. 3,387,501; 4,120,212; and 4,296,642 disclose the use of pin and/or ball type interlock mechanisms. Examples of locking plate type interlock mechanisms can be found in U.S. Pat. Nos. 3,929,029 and 4,132,125.
While the prior art interlock mechanisms have performed satisfactorily, many of these mechanisms are relatively complicated and difficult to manufacture.